I am in a little problem, theres a problem in one of the components, is a new component that we are working with the leads are tin coated, and after we solder in the reflow oven, with lead solder, we took them to do a some test and on a cross section they find that there was no intermetallic layer, these is coming one out of every ten !, they took a picture in 1000X and you can see a thin layer between the lead of the component and the solder this is in the good ones, on the bad ones you cant see that layer, can someone knows why this happen? and where I can find documentation on the problem?